This is the inside account of the secret battle US Marines have been fighting against ISIS

Maj. David Palka had seen combat in Iraq and Afghanistan, but roughly 90% of the Marines under his command, tasked with setting up a remote fire base in northern Iraq in 2016, had only heard the stories.

Their trial by fire in March 2016 came just hours after they landed on Army CH-47 helicopters under cover of darkness in Makhmur, Iraq. Getting off the helicopters at around 2 a.m., the Marines were in what was essentially open farmland with a large protective berm of dirt around their small perimeter.

“By 0900, we received the first rocket attack,” Palka told Business Insider.

As a captain, Palka had led the Marines of Echo Battery, 2nd Battalion, 10th Marine Regiment when it was attached to the 26th Marine Expeditionary Unit from October 2015 to June 2016.